Effects of cadmium and high-fat diet on essential metal concentration in the mouse testis

Changes of N6-methyladenosine and ferroptosis in cadmium-induced reproductive toxicity of male mice fed a high fat and high sugar diet

Cadmium (Cd) and high-fat and high-sugar diet (HFHS) are risk factors contributing to the decline in male sperm quality. N6-methyladenosine (m6A) is essential in the processes of testicular development and spermatogenesis. Ferroptosis, a form of cell death that depends on iron, is prone to causing testicular dysfunction. However, the changes in m6A modification regulatory proteins and ferroptosis signaling molecules in male mice with sperm abnormalities resulting from combined exposure to Cd and HFHS remain incompletely elucidate. Our present data indicate that the combined treatment of Cd and HFHS significantly reduced sperm quality in comparison to those in single Cd or HFHS treatment. In addition, indicators related to ferroptosis in the combined treatment of Cd and HFHS group have also undergone significant changes. In detail, the contents of malondialdehyde (MDA) and Fe2+ as well as Slc7a11 expression were increased while Gclc expressions were reduced in the testicular tissue of Cd and HFHS combined treatment mice. Further detect results showed that the combined exposure to Cd and HFHS synergistically elevated the m6A modification levels alongside a downregulation of the Mettl3, Fto, Alkbh5 and Ythdc2 at the protein level when compared with those in single Cd or HFHS treatment. Altogether, it can be inferred that Cd and HFHS combined treatment may alter the levels of m6A modification regulatory proteins in testicular tissue, leading to increased Fe2+ and MDA production, thus activating the Slc7a11/Gpx4 signaling pathway, ultimately decreasing the sperm quality in mice, providing preliminary evidence for the occurrence of ferroptosis in testicular cells. Our findings may provide direction for the study of reproductive toxicity of cadmium and offer reference for the selection of molecular targets.

Adolescent co-exposure to environmental cadmium and high-fat diet induces cognitive decline via Larp7 m6A-mediated SIRT6 inhibition

The effects and underlying mechanisms of adolescent exposure to combined environmental hazards on cognitive function remain unclear. Here, using a combined exposure model, we found significant cognitive decline, hippocampal neuronal damage, and neuronal senescence in mice exposed to cadmium (Cd) and high-fat diet (HFD) during adolescence. Furthermore, we observed a significant downregulation of Sirtuin 6 (SIRT6) expression in the hippocampi of co-exposed mice. UBCS039, a specific SIRT6 activator, markedly reversed the above adverse effects. Further investigation revealed that co-exposure obviously reduced the levels of La ribonucleoprotein 7 (LARP7), disrupted the interaction between LARP7 and SIRT6, ultimately decreasing SIRT6 expression in mouse hippocampal neuronal cells. Overexpression of Larp7 reversed the combined exposure-induced SIRT6 decrease and senescence in mouse hippocampal neuronal cells. Additionally, the results showed notably elevated levels of Larp7 m6A and YTH domain family protein 2 (YTHDF2) in mouse hippocampal neuronal cells treated with the combined hazards. Ythdf2 short interfering RNA, RNA immunoprecipitation, and RNA stability assays further demonstrated that YTHDF2 mediated the degradation of Larp7 mRNA under combined exposure. Collectively, adolescent co-exposure to Cd and HFD causes hippocampal senescence and cognitive decline in mice by inhibiting LARP7-mediated SIRT6 expression in an m6A-dependent manner.

Sperm Rhoa m6A modification mediates intergenerational transmission of paternally acquired hippocampal neuronal senescence and cognitive deficits after combined exposure to environmental cadmium and high-fat diet in mice

Little is currently known about the effect and mechanism of combined paternal environmental cadmium (Cd) and high-fat diet (HFD) on offspring cognitive ability. Here, using in vivo model, we found that combined paternal environmental Cd and HFD caused hippocampal neuronal senescence and cognitive deficits in offspring. MeRIP-seq revealed m6A level of Rhoa, a regulatory gene of cellular senescence, was significantly increased in combined environmental Cd and HFD-treated paternal sperm. Interestingly, combined paternal environmental Cd and HFD markedly enhanced Rhoa mRNA, its m6A and reader protein IGF2BP1 in offspring hippocampus. STM2457, the inhibitor of m6A modification, markedly mitigated paternal exposure-caused the elevation of hippocampal Rhoa m6A, neuronal senescence and cognitive deficits in offspring. In vitro experiments, Rhoa siR significantly reversed mouse hippocampal neuronal senescence. Igf2bp1 siR obviously reduced the level and stability of Rhoa in aging mouse hippocampal neuronal cells. In conclusion, combined paternal environmental Cd and HFD induce offspring hippocampal neuronal senescence and cognitive deficits by promoting IGF2BP1-mediated Rhoa stabilization in offspring hippocampus via elevating Rhoa m6A in paternal sperm.

Impact of Cadmium and Lead Exposure on Camel Testicular Function: Environmental Contamination and Reproductive Health

The free grazing habits of camels from various sources may cause heavy metals to bioaccumulate in their tissues and organs, possibly resulting in higher amounts of these toxic substances in their bodies over time. The aim of this study was to assess the exposure impact of lead (Pb) and cadmium (Cd) on bull camels of the Lassi breed, aged 7 to 8 years, at a site near the industrial area and another two non-industrial sites, to analyze the presence of heavy metals. Samples from three sites were collected from thirty camels (n = 10/each), soil and water (n = 30), and five different plants (n = 15/each) for analysis. Testes were collected for atomic absorption spectrometry (AAS), and hematoxylin-eosin (HE) staining. Serum samples were obtained to measure testosterone levels by radioimmunoassay (RIA). Samples were obtained from plants, soil, water, blood, serum and urine for AAS. According to the results, the testes' weight, length, width, and volume significantly decreased at the industrial site compared with the other two sites as a result of exposure to Cd and Pb. Additionally, blood testosterone concentrations were considerably lower at the industrial site, indicating a detrimental impact on testicular steroidogenesis. The histological investigation of the industrial site indicated structural disturbances, including seminiferous tubule degeneration and shedding, cellular debris in seminiferous tubules, lining epithelium depletion, and vacuolation. Elevated amounts of Cd and Pb were found at the industrial site when analyzed using water, soil, plants, testes, serum, and urine. These findings demonstrate the adverse effects of Pb and Cd exposure on camel testicular function, including decreased weight and altered steroidogenesis. These findings are essential for understanding the impact of exposure to Pb and Cd on camel reproductive function and for developing successful prevention and management plans for these exposures in this species.

Combination of high-fat diet and cadmium impairs testicular spermatogenesis in an m6A-YTHDF2-dependent manner

Environmental cadmium (Cd) or high-fat diet (HFD) exposure alone are risk factors of male infertility. However, the effect and mechanism of co-exposure to HFD and Cd on sperm quality remain unclear. This study was aimed to explore the combined effects of HFD and Cd on spermatogenesis as well as its m6A-dependent mechanism in vivo and in vitro. As a result, co-exposure of HFD and Cd resulted in a significant decrease in the number of mature testicular seminiferous tubules and epididymis sperm quantity in mice, compared with Cd or HFD exposure alone. Correspondingly, the mRNAs expression of Smc3(spermatocytes marker), Acrv1(round spermatids marker) and Lzumo3(elongated spermatids marker) were downregulated in HFD and Cd group. Furthermore, combined exposure downregulated the expression of meiosis-related proteins (STRA8 and SYCP3), increased the m6A level of Stra8, and upregulated the expression of m6A-related proteins (METTL3 and YTHDF2) in mouse spermatocytes. Mechanistically, the above-mentioned impacts caused by co-exposure were markedly restored by Mettl3 siR and Ythdf2 siR. In addition, RNA stability assay showed that Ythdf2 siR obviously reversed co-exposure-increased Stra8 mRNA degradation rate in actinomycin-D-treated mouse spermatocytes. Meanwhile, excess ROS was observed in combined-exposure group, and a free radical scavenger N-tert-Butyl-α-phenylnitrone (PBN) attenuated co-exposure-upregulated expression of METTL3 and YTHDF2 in mouse spermatocytes. These results suggested that combination of HFD and Cd impaired spermatogenesis by degrading Stra8 in an m6A-YTHDF2-dependent manner via ROS activation.

Effects of whole-life exposure to low-dose cadmium with post-weaning high-fat diet on offspring testes in a male mouse model

Although several studies have reported testicular impairments caused by cadmium (Cd) or obesity alone, the combined effect of Cd and obesity on the testes and its underlying mechanism remains unclear. We examined the combined effect of whole-life exposure to low-dose Cd started at preconception and post-weaning high-fat diet (HFD) on the testes of offspring mice. At weaning, male offspring parented with and without exposure to low-dose Cd were continued on the same drinking water regimen as their parents and fed with either a normal diet (ND) or HFD for 10 or 24 weeks. Whole-life exposure to Cd resulted in its accumulation in testes, and HFD induced obesity and lipid metabolism disorder. Exposure to Cd or HFD alone significantly decreased Johnsen scores, disrupted testicular structure, and increased germ cell apoptosis at both 10 and 24 weeks. However, co-exposure to Cd and HFD did not induce the toxic effects that were induced by either alone, as revealed by preserved testicular structure and spermatogenesis, lack of significant apoptosis, and increased cell proliferation. Mechanistically, the combined effects of low-dose Cd and HFD consumption were associated with the activation of the JAK/STAT pathway. These findings suggest that co-exposure to low-dose Cd and HFD did not cause Cd- or HFD-induced testicular injury, probably because of the activation of the JAK/STAT pathway to prevent germ cell apoptosis.

Cadmium-Induced Kidney Injury: Oxidative Damage as a Unifying Mechanism

Cadmium is a nonessential metal that has heavily polluted the environment due to human activities. It can be absorbed into the human body via the gastrointestinal tract, respiratory tract, and the skin, and can cause chronic damage to the kidneys. The main site where cadmium accumulates and causes damage within the nephrons is the proximal tubule. This accumulation can induce dysfunction of the mitochondrial electron transport chain, leading to electron leakage and production of reactive oxygen species (ROS). Cadmium may also impair the function of NADPH oxidase, resulting in another source of ROS. These ROS together can cause oxidative damage to DNA, proteins, and lipids, triggering epithelial cell death and a decline in kidney function. In this article, we also reviewed evidence that the antioxidant power of plant extracts, herbal medicines, and pharmacological agents could ameliorate cadmium-induced kidney injury. Finally, a model of cadmium-induced kidney injury, centering on the notion that oxidative damage is a unifying mechanism of cadmium renal toxicity, is also presented. Given that cadmium exposure is inevitable, further studies using animal models are warranted for a detailed understanding of the mechanism underlying cadmium induced ROS production, and for the identification of more therapeutic targets.